Bifunctional reactive pentamethine cyanine dyes for biomedical applications

New unsymmetrical pentamethine cyanine dyes containing two non-equivalent reactive groups selected from carboxyl, amino and hydroxyl in different combinations were synthesized and their spectral properties investigated. Amino and hydroxy groups were used for binding the dyes to the anticancer drug, chlorambucil (CLB) via biodegradable amide or ester linker while the second reactive functionality could be utilized for attachment at mild conditions to a targeting carrier such as an antibody or peptide. These conjugates can thereby potentially be suitable for fluorescence-based monitoring of drug delivery. The CLB release profiles triggered by biodegradable linker were investigated in buffer solutions and cell medium using LC-MS and spectrofluorimetric methods.